The present invention relates in general to heat recovery steam generators and in particular to a new and useful barrier for blocking a gas lane between modules of a steam generator.
Typically, in the steam generator field, heat recovery steam generators comprise a casing or box-type structure having vertically oriented finned tube pressure parts which form the heat exchanger. High temperature turbine exhaust gas is passed through the casing and over the finned tubes in order to recover heat from the gas.
One popular configuration for a heat recovery steam generator comprises a modular design which utilizes a pre-fabricated and pre-assembled heating surface arrangement. The heat exchangers are manufactured in modules and are arranged side-by-side within a casing. Each module has a frame for handling and field expedient purposes. However, when the modules are positioned adjacent each other in a casing, gas lanes or passages are formed between the modules due to the steel frames of each module. In an effort to maintain the efficiency of the boiler, the gas lanes must be blocked and the gas forced through the heating surface arrangement, which normally comprises spiral finned tubes.
The current solution to the gas lane problem is to employ baffles, made of a light gage sheet metal, that are welded either to the fins of the heating surface or to the frame of each module. It is very common for the gas lane baffles to be welded directly to the spiral fin tubes because of the inaccessibility of the steel frames of the modules. This solution to the gas lane problem has proved to be very costly for field installation and is not very reliable.